Proton Temperature Gradients From 0.3 to 1 AU

Helios spacecraft proton temperature data excluding ejecta intervals are sorted into bins of heliocentric distance. The distribution of temperatures within each distance bin from the coldest to hottest temperatures is further subdivided into bins. For each relative temperature bin fIts for the mean temperature as a function of heliocentric distance are made assuming a power law. The range of power indices is similar to those found by solar wind speed binning. Temperature gradient measurements are applied to evaluate the proton equation of state and estimate the proton heating rate in the solar wind. This heating rate is compared with turbulent energy cascade rates.